In theory, who doesn’t believe in self-determination, the idea, developed in the 19th century, that all nations have a right to sovereignty? By the early 20th century, President Woodrow Wilson was insisting that “National aspirations must be respected; people may now be dominated and governed only by their own consent.” In theory, self-determination is today a fundamental principle of international law.

In practice, not so much. The Middle East’s 35 million Kurds have long wanted their own nation-state. They’re not about to get one anytime soon. The government of Spain is determined to quash the movement for Catalonian independence. China prohibits even discussions of Tibet’s right to break free.

What brings these issues to mind now? On Nov. 2 it will be exactly 100 years since the Balfour Declaration, the British Empire’s statement in support of the establishment of “a national home for the Jewish people” in Palestine, then a backwater of the soon-to-be-defeated Ottoman Empire.

Britain’s promise enjoyed what historian Martin Kramer calls “buy-in” from the Allied Powers, including the U.S. and France, who fought the Central Powers, including Germany and the Ottomans, in what we retrospectively call World War I.

“In Palestine shall be laid the foundation of a Jewish Commonwealth,” President Wilson announced. French diplomat Jules Cambon wrote that it would be “a deed of justice and of reparation to assist, by the protection of the Allied Powers, in the renaissance of the Jewish nationality in that Land from which the people of Israel were exiled so many centuries ago.”

The Zionist cause was soon endorsed by the broader international community as well. It was incorporated into the mandate for Palestine given to Britain by the League of Nations in the 1920s. Mr. Kramer notes: “Those who now cast the Balfour Declaration as an egregious case of imperial self-dealing simply don’t know its history (or prefer not to know it).”

Also too often forgotten or ignored is the fact that it was thanks to Britain and the other Allied Powers that Arab nation-states rose from the Ottoman ashes. Among them: Lebanon, Syria, Iraq, Saudi Arabia, Jordan, Kuwait, Bahrain, Qatar and Yemen.

A related anniversary: On Nov. 29, it will be 70 years since the United Nations recommended partitioning western Palestine (the east became the Hashemite Kingdom of Jordan) into two independent states, one Arab and one Jewish. Note: In that era, both Arabs and Jews were equally “Palestinian.”

Jewish leaders accepted partition. Arab leaders rejected it. In May 1948, upon termination of the British mandate, those Jewish leaders declared independence and won recognition from the U.S., the Soviet Union and other U.N. members.

Five Arab nations launched what became known as the First Arab-Israeli War. The Arab League’s secretary-general, Azzam Pasha, promised it would be “a war of extermination and a momentous massacre which will be spoken of like the Mongolian massacres and the Crusades.”

But the Jews, who had nowhere else to go and the memory of the Holocaust fresh in their minds, managed to hold their ground. In February 1949 an armistice was declared. After that, Arab and Muslim nations might have granted their own Jewish communities basic rights and freedoms. They could then have made the case that the Jewish state was superfluous. Instead and vindictively, those Arab and Muslim governments more harshly persecuted their Jewish subjects, confiscating their properties and, before long, driving them out.

More than 800,000 Jews ended up fleeing Arab and Muslim countries. A majority were resettled in Israel where, over time, they strengthened the nation. Today, roughly half of all Israelis are descendants of Jews from the broader Middle East — Morocco to Iraq (Baghdad was close to a third Jewish as recently as 1945) to Afghanistan. Slightly fewer Palestinians, an estimated 700,000, fled Israel, many going to Arab countries that chose not to assimilate or even integrate them.

A third anniversary: In 1967, Egypt, Syria and Jordan waged another war intended to drive the Jews into the sea. The Israelis not only survived, they seized Gaza from Egypt, and the West Bank (earlier known as Judea and Samaria) from Jordan. Over the years since, the possibility of transforming these territories into an independent Palestinian state — the “two-state solution” — has been the basis for one peace plan after another.

None has succeeded. I’d argue that the primary reason is that Palestinian leaders are still fighting wars of the past. They refuse to recognize the legitimacy of Israel under international law, the necessity for Israel given the durability of Jew-hatred, and the reality of Israel established and defended by “blood and iron.”

Throughout 2017, Palestinian Authority President Mahmoud Abbas and other Palestinian leaders have been denouncing the Balfour Declaration as a “crime,” demanding that the British renounce it and apologize for it.

But British Prime Theresa May said last week that Britons are “proud of the role that we played in the creation of the State of Israel and we certainly mark the centenary with pride.” A separate British government statement asserted that the “important thing now is to look forward and establish security and justice for both Israelis and Palestinians through a lasting peace.”

Who doesn’t want self-determination for the Palestinians? Who doesn’t want to see Palestinians living in freedom and prosperity? That could have begun 70 years ago. It could begin tomorrow. In theory, it would require only willingness on the part of Palestinians to accept and peacefully coexist alongside the “national home for the Jewish people” envisaged by the Balfour Declaration. In practice, such a change of heart might be another hundred years away.

• Clifford D. May is president of the Foundation for Defense of Democracies and a columnist for The Washington Times.